Except the live wire is the one that’s switched. So if you plug it in backwards, the neutral is the one that’s switched. And if they aren’t careful with how the wiring is done, you potentially have live voltage on the outside of your metal cased device.
For another example, your standard e26 bulb can have part of the thread exposed. If the neutral and live are swapped, that threaded bit is hooked to live, instead of the proper neutral.
Neither one of this are issues. Devices need to be manufactured so that you cannot touch potentially live connections if they are connected to sockets.
You think all the knock off overseas manufacturers are adhering to this religiously? Belt and braces works fine for me in this case.
I also saw British plugs from China that had no fuse in it (just a plug adapter that was attached to the charger).
It’s better to just assume neither conductor can be touched.
There is no use case touching neutral conductors or neutral connected metal cases. No functionality is lost by having devices be double insulated, and in practice most if not all devices on the UK market are made to also be marketable in countries with non-polar connectors.
Irrelevant. If neutral gets disconnected, your hypotetical device will have hot case anyway. That is why devices without grounding have to be double insulated